Class MigrationAutodetector
Take a pair of ProjectStates and compare them to see what the first would need doing to make it match the second (the second usually being the project's current state).
Declaration
class MigrationAutodetector
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Note that this naturally operates on entire projects at a time,
as it's likely that changes interact (for example, you can't
add a ForeignKey without having a migration to add the table it
depends on first). A user interface may offer single-app usage
if it wishes, with the caveat that it may not always be possible.
Methods
▷ def __init__(self, from_state, to_state, questioner=None) ▷ def add_operation(self, app_label, operation, dependencies=None, beginning=False) ▷ def arrange_for_graph(self, changes, graph, migration_name=None) Take a result from changes() and a MigrationGraph, and fix the names and dependencies of the changes so they extend the graph from the leaf nodes for each app.
▷ def changes(self, graph, trim_to_apps=None, convert_apps=None, migration_name=None) Main entry point to produce a list of applicable changes. Take a graph to base names on and an optional set of apps to try and restrict to (restriction is not guaranteed)
▷ def check_dependency(self, operation, dependency) Return True if the given operation depends on the given dependency, False otherwise.
▷ def deep_deconstruct(self, obj) Recursive deconstruction for a field and its arguments. Used for full comparison for rename/alter; sometimes a single-level deconstruction will not compare correctly.
▷ def generate_altered_fields(self) Make AlterField operations, or possibly RemovedField/AddField if alter isn's possible.
▷ def generate_altered_options(self) Work out if any non-schema-affecting options have changed and make an operation to represent them in state changes (in case Python code in migrations needs them).
operations for them as well as separate operations to create any
foreign key or M2M relationships (these are optimized later, if
possible).
Defer any model options that refer to collections of fields that might
be deferred (e.g. unique_together, index_together).
▷ def generate_created_proxies(self) Make CreateModel statements for proxy models. Use the same statements as that way there's less code duplication, but for proxy models it's safe to skip all the pointless field stuff and chuck out an operation.
operations for them as well as separate operations to delete any
foreign key or M2M relationships (these are optimized later, if
possible).
Also bring forward removal of any model options that refer to
collections of fields - the inverse of generate_created_models().
▷ def generate_renamed_models(self) Find any renamed models, generate the operations for them, and remove the old entry from the model lists. Must be run before other model-level generation.
▷ def only_relation_agnostic_fields(self, fields) Return a definition of the fields that ignores field names and what related fields actually relate to. Used for detecting renames (as the related fields change during renames).
▷ def swappable_first_key(self, item) Place potential swappable models first in lists of created models (only real way to solve #22783).
Class methods
▷ def parse_number(cls, name) @classmethod Given a migration name, try to extract a number from the beginning of it. If no number is found, return None.
@classmethod
def parse_number(
cls,
name,
)
Reexports